Hi there,
If your REALLY need to have PNGs with alpha transparency, the only way is using them inside a Flash movie, cuz Macromedia Flash is the only program (as far as I know) who can handle it.
Save as 24-bit + transparency PNG. Import into Flash.

The reason one uses PNGs rather than GIFs is not only because the compression, colour depth and other techy things are better than GIFs, but also for ethical and legal reasons. Unisys hold a patent on the LZW compression algorithm which the GIF uses, and to make software that can use GIFs you have to pay Unisys a great whack of money. Whereas PNGs are public tender, so you can use them at will without any lisencing problems!